1. Field of the Disclosure
This disclosure relates to a polymer for immersion lithography and a photoresist composition containing the same for obtaining a fine pattern in the manufacture of semiconductor devices.
2. Description of Related Technology
A currently used lithography process is a dry lithography process which employs an exposure system where a space between an exposure lens and a wafer is filled with air. In order to develop a device to 60 nm resolution using dry lithography, a new exposure system using light sources such as a F2 laser (157 nm) or extreme ultraviolet (EUV) laser is required. However, it is difficult to develop a pellicle when the F2 laser is used, and to develop a mask and light sources when the EUV laser is used.
Immersion lithography has been developed in order to overcome the above-described problems.
In immersion lithography, a suitable aqueous solution fills a space between a projection lens and a wafer, thereby increasing numerical aperture of optics corresponding to the refractive index of the solution. The actual wavelength of the light source in the solution is equivalent to a value calculated by dividing a wavelength of the light source in the air by the refractive index of the solution. For example, if water of which the reflective index is 1.44 is used as a medium, 193 nm wavelength of ArF light source is converted into 134 nm. This is the same effect when a light source having a shorter wavelength such as a F2 laser (157 nm) is used to increase resolution.
However, since a space between projection lens and wafer is filled not with air but with an aqueous solution in conventional immersion lithography, a photoacid generator present in the photoresist may be dissolved in the aqueous solution, resulting in the contamination of an exposure lens and the deformation of the photoresist pattern.